When selection start with <br/> element, the getRangeCfiFromDomRange() return wrong range cfi

[JackieFei]

This issue is a Bug

Expected Behaviour

get correct range cfi

Observed behaviour

Readium return the contentCFI:"/4[x9-8000]/6/4,,/7:13” which start cfi is empty

Steps to reproduce

1. open https://readium.firebaseapp.com/?epub=epub_content%2Flinear-algebra&
2. jump to Chapter 1. Theorems
3. make a selection as below: ( Note: must start selection at blank area !! )
   
4. open developer tool console, enter 5 commands:
   var sel = document.getElementsByTagName('iframe')[0].contentDocument.getSelection()
   var range = document.getElementsByTagName('iframe')[0].contentDocument.createRange()
   range.setStart(sel.anchorNode,sel.anchorOffset)
   range.setEnd(sel.focusNode,sel.focusOffset)
   ReadiumSDK.reader.getRangeCfiFromDomRange(range)
5. the returned range cfi is "/4[x9-8000]/6/4,,/7:13" (start cfi is empty)
   

Product

Readium cloud reader app

Additional information

Maybe caused by self-closing tags

[danielweck]

I assigned @jccr just as a heads-up, just in case there is already a fix via another issue or pull request.
Related: #353 and #353